1.Field of the Invention
The present invention relates to a local network of industrial or domestic type intended for the control and/or the supervision of various appliances by means of one or several distributed (or delocalized) computers.
2.Discussion of the Related Art
FIG. 1 very schematically illustrates the architecture of an industrial or domestic network. Network N enables connection of several devices, three devices D1, D2, D3 being shown in FIG. 1. Each device is for example formed of a computer, of an actuator controlled by a microprocessor or of a sensor connected to a microprocessor. Each device D1, D2, D3 comprises an application system A1, A2, A3 and a communication circuit C1, C2, C3. Communication circuit C1, C2, C3 may comprise a microprocessor or a programmable logic and ensures the reception and the transmission of information frames over network N. Application system A1, A2, A3 comprises a microprocessor or a programmable logic which, under control of a program that may be modified by a user, processes the information frames transmitted and received by communication circuit C1, C2, C3. Application system A1, A2, A3 may further be connected to actuators or sensors. Application system A1, A2, A3 and communication circuit C1, C2, C3 may be formed by separate integrated circuits connected by wire links W.
Generally, application system A1, A2, A3 sets up the information frames sent to communication circuit C1, C2, C3 according to operating parameters of network N so that they can be properly transmitted over network N by communication circuit C1, C2, C3. The network operating parameters are the set of parameters which define the data flows over the network, the priorities between the devices connected to the network, the shape of the information frames transmitted over the network, etc. The information frames may also be directly set up by communication circuit C1, C2, C3 according to the network operating parameters which are set by application system A1, A2, A3 and which can be modified by it.
A disadvantage is that by modifying the elements forming application system A1, A2, A3 of a device D1, D2, D3 connected to network N, for example, by modifying the program executed by the microprocessor of application system A1, A2, A3, it is possible to modify the network operating parameters used by device D1, D2, D3 and thus to alter, or even to interrupt the operation of network N. It may then be difficult to find out the origin of the anomaly and to correct it, and the network may be definitely deteriorated. Similarly, when a new device is connected to network N, it is assumed that the application system of the new device has network operating parameters which are adapted to the network N to which the device is connected. In the case where such parameters are incorrect, the new device connected to network N can alter, or even interrupt, the general operation of network N.